philosophizing on discrete-event sim. disable intersection merging; it's

mostly incorrect and needs lots more thought.

docs/design/discrete_sim.md

@@ -0,0 +1,42 @@
+# Discrete simulations
+
+## Why are timesteps bad?
+
+Discrete-time sim has two main problems:
+
+1) It's fundamentally slow; there's lots of busy work.
+
+2) Figuring out acceleration in order to do something for the next tick is complicated.
+
+Discrete-event sim is the real dream. I know when a ped will reach the end of a
+sidewalk and can cheaply interpolate between for drawing. If I could do the
+same for all agents and states/actions, I could switch to discrete-event sim
+and SUPER speed up all of the everything.
+
+This possibly ties into the FSM revamp idea perfectly. Every state/action has
+two durations associated with it:
+
+- the best case time, calculated while pathfinding, which assumes no
+  conflicts/delays due to scarcity
+- the actual time something will take, based on state not known till execution
+  time
+
+## Intent-based kinematics
+
+Instead of picking acceleration in order to achieve some goal, just state the
+goals and magically set the distance/speed based on that. As long as it's
+physically possible, why go through extra work?
+
+Lookahead constraints:
+- go the speed limit
+- dont hit lead vehicle (dist is limited by their dist + length + following dist)
+- stop by a certain point
+
+## The software engineering question
+
+Is there a reasonable way to maintain both models and use one headless/editor
+for them? Seemingly, the entire Sim API needs to just be abstracted. Like the
+DrawAgents trait, but a bit more expanded. Except stuff like time travel
+applied to discrete-time sim can't support debugging agents or showing their
+path. I think time travel with discrete-event would work fine -- just storing
+all the previous states with the exact times.

docs/design/intersections.md

@@ -117,3 +117,7 @@ Maybe start by hardcoding the things to merge. Don't worry about detection yet.
 	- extend two roads with points from the tiny road. delete i283
 	- make sure the road attributes match up
 	- do this first; preprocess raw_data.
+
+Ah, the problem with just extending geometry... I think turns need to be
+polylines sometimes. Need to do the merging all the way at the end,
+unfortunately...

docs/design/testing.md

@@ -76,3 +76,5 @@ Synthetic editor is awesome. How could it help test setup?
 	- for sim tests, print a command to run it in the UI
 
 Let's experiment and make a new binary crate for all tests!
+
+- it'd be neat to later integrate with travis.

map_model/src/map.rs

@@ -66,7 +66,9 @@ impl Map {
     ) -> Map {
         timer.start("raw_map to Map");
 
-        make::merge_intersections(&mut data, timer);
+        if false {
+            make::merge_intersections(&mut data, timer);
+        }
 
         let gps_bounds = data.get_gps_bounds();
         let bounds = gps_bounds.to_bounds();